Pyrrole and aniline are monomers that can form a conjugated polymer structures that are electrically conducting. These conducting polymers have become useful in a number of applications. Uses of commercial importance include shielding for electromagnetic radiation, electro-optic devices including storage and transmission applications, high energy density batteries, microelectronic devices, electrochromic windows, displays, sensors, and indicators, electromechanical actuators, semiconductor circuits, redox capacitors, gas separation, and controlled chemical delivery systems.
Both polypyrrole and polyaniline can be formed by chemical or electrochemical techniques. For example, polypyrrole can be electropolymerized from aqueous solutions containing 0.1M pyrrole (C.sub.4 H.sub.4 NH) and 0.1M tosylate (CH.sub.3 (C.sub.6 H.sub.4)SO.sub.3 Na) and from nonaqueous acetonitrile solutions with 1% water by volume, where silver nitrate (AgNO.sub.3) is the supporting electrolyte. These polymer films may be deposited on platinum and gold working electrodes galvanostatically using an applied current density of 2.0-4.0 mA cm.sup.-2.
Photopolymerized films of polypyrrole and polyaniline are prepared from solutions containing pyrrole or aniline monomers, along with various additives, such as electron acceptors, photoinitiators and flexibilizers, dissolved in the pure monomer to accelerate the polymerization process and to improve the quality of the resulting films. Electron acceptors included silver salts, AgNO.sub.3, AgTs (Ts=CH.sub.3 (C.sub.6 H.sub.4)SO.sub.3.sup.-, tosylate) and AgBF.sub.4, added in amounts of 1-20 mole % (moles electron acceptor)/(moles of monomer+moles of electron acceptor). A thin layer of the formulation is cast and evenly spread on the surface of a selected substrate, such as aluminum, gold, platinum, ceramic, glass, paper, Teflon, Mylar and polystyrene substrates, which is subsequently placed under the output of a UV lamp. Curing is performed under strictly controlled illumination conditions. Multiple coating-curing cycles may be carried out in order to produce thick uniform films.
Solutions of the photopolymerization formulations described above must be stored in glass vials that exclude the penetration of light. However, because a slow chemical polymerization takes place in the presence of Ag.sup.+ ions over a period of only about 1-2 days, it is generally desirable to prepare a fresh batch of the photopolymerization formulation immediately prior to use.
Therefore, there is a need for a photopolymerization formulation of pyrrole and/or aniline that can be stored over extended periods of time without polymerizing. It would be desirable if the formulation were concentrated to minimize storage.